This flow shows choosing a base image, deciding if a minimal image is suitable, building with only needed packages, and checking the final image size.
Execution Sample
Docker
FROM alpine:3.18
RUN apk add --no-cache curl
CMD ["curl", "--version"]
This Dockerfile uses a minimal Alpine base image, adds curl without cache to keep size small, and runs curl version command.
Process Table
Step
Action
Image Size (MB)
Description
1
Start with alpine:3.18 base image
5
Alpine is a minimal Linux image (~5MB)
2
Run apk add --no-cache curl
7
Adds curl package without cache, small size increase
3
Set CMD to run curl --version
7
No size change, sets default command
4
Build final image
7
Final image size is about 7MB, very small
5
Compare with ubuntu base image
29
Ubuntu base image is much larger (~29MB)
6
Exit
-
Finished building minimal image
💡 Build finished with minimal base image resulting in a small final image size
Status Tracker
Variable
Start
After Step 2
After Step 3
Final
Image Size (MB)
5 (alpine base)
7 (after curl install)
7 (after CMD set)
7 (final image)
Key Moments - 3 Insights
Why does using alpine base image reduce image size compared to ubuntu?
Alpine is designed to be minimal and small (~5MB), while Ubuntu includes many packages by default making it larger (~29MB), as shown in execution_table rows 1 and 5.
What does --no-cache do in apk add command?
It prevents caching package index files, so they are not saved in the image, keeping the image size smaller, as seen in step 2 where size only increases slightly.
Does setting CMD affect image size?
No, setting CMD only defines the default command to run and does not change the image size, as shown in step 3.
Visual Quiz - 3 Questions
Test your understanding
Look at the execution table, what is the image size after adding curl to alpine?
A5 MB
B7 MB
C29 MB
D12 MB
💡 Hint
Check the 'Image Size (MB)' column at step 2 in the execution_table
At which step does the image size increase from the base image size?
AStep 2
BStep 3
CStep 1
DStep 5
💡 Hint
Look for the first step where 'Image Size (MB)' changes from 5 to 7 in execution_table
If we used ubuntu base image instead of alpine, what would be the approximate base image size?
A5 MB
B7 MB
C29 MB
D50 MB
💡 Hint
Refer to step 5 in execution_table comparing ubuntu base image size
Concept Snapshot
Use minimal base images like alpine (~5MB) to keep Docker images small.
Add only needed packages with no cache to avoid size bloat.
Standard images like ubuntu are larger (~29MB).
Setting CMD does not affect image size.
Check image size after build to confirm minimal footprint.
Full Transcript
This lesson shows how choosing a minimal base image like alpine reduces Docker image size compared to standard images like ubuntu. We start with alpine base image of about 5MB. Adding curl with apk add --no-cache increases size slightly to about 7MB. Setting CMD does not change size. The final image remains small and efficient. Using no-cache prevents extra files from being saved, keeping the image lean. Comparing with ubuntu base image shows it is much larger at about 29MB. This teaches how minimal base images and careful package installation help keep Docker images small and fast to deploy.